Changing the FS Type of the Root Partition

There may be a time when you need to change the file system type used on your
root partition. This might be because you want to get better performance or
better stability/reliability. Or, it might be because a new release of the
kernel isn't able to mount one or more of your current partitions.

For me, it was the latter event that caused me to migrate the partition used
for root and a data partition from being in XFS format to using EXT3 (for the
root partition) and JFS (for the data partition). I wanted to move away from
XFS because at the time of this writing, the 2.6.22 kernel for Linkstations
was having stability problems with XFS.

As such, you will see that the following procedure actually changes two
partitions. Depending you your needs, you might not have to do all of the
steps. For example, if your second partition already uses the desired FS
type and has enough unused space, then Step 1 and Step 18 can be skipped.
Similarly, if your current kernel does everything you need, then Step 15 can
be avoided.

I chose EXT3 for the partition holding root because first it is journaled.
Second, and more importantly, it is a FS type that can be mounted while in
EM. This means that I can use EM as part of the process. And, once this is
done, I will have a chance to use EM to fix most of the errors I might make while
playing with the system in the future.

Warning: messing with the root partition is not something to be done lightly.
You can get your machine into a state such that it will not boot. Fortunately
I don't think you can brick your box doing this, but you can make it painful
to recover.

So, please read and understand the procedure before beginning, and be sure to
backup any critical data. This is not a complicated process but it is
lengthy. And given that data are wiped clean from the partition at a point
in the flow it will pay to not rush things.

(Thanks go to Dave and MoonMaker for helping me get the kinks out of this.)

Here we can see that /dev/sda6 currently is being mounted using XFS. We will
have to reformat this partition since we want to use this partition as the holding place
for the copy of the root partition. (If this partition is formated as EXT3, then you
will not have to reformat it.)

Note that this fstab file does not specify the partition to be mounted at /.